Since the introduction of LEDs, they have primarily been used as indicator lights in various electronic systems. However, their applications extend far beyond simple indication. In this article, we’ll explore a few common and practical uses of LEDs in different circuits.
(1) One typical application is using an LED with a three-terminal voltage regulator like the 7805. By adding an LED to the circuit, you can not only increase the output voltage slightly but also use it as a power indicator. This is shown in the diagram below.
(2) LEDs are also widely used in AC circuits, such as 220V, 50Hz mains power. They can serve as indicators for electrical work or to signal when a fuse has blown. The schematic on the right illustrates this usage.
When using an LED in an AC circuit, it's important to calculate the current-limiting resistor correctly. The formula for calculating the resistance R is:
R = (VE - UF) / 2 * IF
Where: - VE is the RMS voltage of the AC supply (e.g., 220V), - UF is the forward voltage drop of the LED, - IF is the operating current of the LED.
(3) Another common use of LEDs is as a relay working indicator in relay circuits. This helps users visually confirm whether the relay is active or not. The figure below demonstrates this setup.
LEDs are versatile components that can be adapted for many different purposes. Whether used as simple indicators or integrated into more complex circuits, they play a crucial role in modern electronics. Understanding how to properly use them ensures both safety and functionality in your designs.
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